I have had this tank in QT for going on 3 weeks. Eating normal, looking normal, swimming ok. QT is 20gal long, ammonia 0, Nitrate & Nitrite I don't test, PH 8.2, plenty of circulation. On Monday he had dark patch on body with a lone white dot. Tuesday it looks like, see picture, white still just that not raised. Anybody seen this B4?